Any of about 30 genera of large seaweeds that make up the order Laminariales (brown algae), found in colder seas. Laminaria, abundant along the Pacific coasts and the British Isles, is a source of commercial iodine. Its stipe (stemlike structure) is 3–10 ft (1–3 m) long. The largest known kelp, Macrocystis, grows up to 215 ft (65 m) long. Its body, which has a large rootlike holdfast, a hollow stipe, and branching blades with hollow gas bladders, resembles that of higher plants. It is rich in minerals and algin, a complex carbohydrate used as an emulsifier to prevent crystal formation in ice cream. Species of kelp are widely eaten in East Asia.

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